1. Field of the Invention
The present invention relates to apparatuses useful for cutting a workpiece. More particularly, the present invention relates to cutting apparatuses useful for cutting workpieces such as shaped metallic strips.
2. Description of the Invention's Background
There are two major standards for devices that enable the mounting of electrical components within an electrical control panel or center, the National Electrical Manufacturing Association (NEMA) standard and the International Electrotechnical Commission (IEC) standard. Under the NEMA standard, which historically has been followed most often in the United States, each electrical component in an electrical control panel or center is bolted into the panel or center. Under the IEC standard, which historically has been followed most often in Europe, one or more DIN rails are bolted into an electrical control panel or center and electrical components are snapped onto the DIN rails. The acronym DIN stands for Deutsches Institut fur Normung. It is a German standard for rails used throughout Europe.
Often many electrical components are located within one control panel or center, and many such components may be snapped onto one length of DIN rail under the,IEC standard. Use of the IEC standard thus can save a manufacturer of control panels or centers, or of equipment having control panels or centers, a significant amount of assembly time as compared to use of the NEMA standard. Accordingly, while the NEMA standard historically has been more dominant in the United States, more and more U.S. manufacturers are beginning to manufacture in accordance with the IEC standard, such that the IEC standard appears to be becoming the dominant standard in the world.
Use of the IEC standard does give rise to a problem, however. DIN rail generally has a nonlinear, relatively complex, thin-walled cross-section, such as the DIN rail cross-sections shown on page 15 of the IBOCO 1995 general catalog, because DIN rail must present surfaces around which electrical components may be snapped. DIN rail normally is manufactured in 6 or 8 foot lengths, and must be cut down to the needed size by a panel or equipment manufacturer assembling an electrical panel or center. Because of the irregular shape of DIN rail, it is difficult if not impossible to cleanly and accurately cut DIN rail without deforming the DIN rail using standard metal shears or cutting tools. Sections of DIN rail to be mounted in a panel may be as small as one inch (25.4 mm) long, and may need to be cut cleanly to within about 1/16" (1.6 mm) to 1/32" (0.8 mm).
A clean, accurate and non-deforming cut is considered to be very important by manufacturers that produce control panels or centers as final products or as parts of final products. It is considered important by such manufacturers that control panels and centers have a very clean look for their customers, and thus that DIN rails extend up to but not beyond the edges of components mounted thereon, and have clean rather than rough, deformed or jagged edges. Deformed DIN rail edges additionally are disadvantageous because they,can cause components not to fit well on the DIN rail, and DIN rails that are deformed more than about 0.01 inch (0.25 mm) generally are not used by the manufacturers. Producing a clean, undeformed and accurate length of DIN rail becomes especially difficult when a length has already been cut to slightly too long a length, and must be trimmed to the correct length.
As stated above, various standard metal-cutting devices are known for cutting or punching metal sheets or strips. For example, U.S. Pat. No. 990,636 to Dalbey, U.S. Pat. No. 2,355,320 to Nebel, U.S. Pat. No. 3,996,831 to Gale, British Patent Publication No. 632,136 and British Patent Publication No. 904,492 disclose various devices having linear- or curvilinear-edged cutters or punches for cutting or punching metal sheets or strips. Such standard devices generally have the disadvantage, however, that they tend to deform a workpiece such as DIN rail that has a relatively complex, thin-walled cross-sectional shape, especially when a short length or the trimming of a length is required.
Other devices are known that are specifically designed to cut complex strip shapes. For example, U.S. Pat. No. 4,457,197 to Wepner, et al. discloses a cutting device wherein an angle section is placed through a die particularly shaped to receive the angle section, and a hydraulically-powered cutting edge is then sheared through the angle section to cut the angle section to a particular length. U.S. Pat. No. 5,142,958 to Nordlin, et al. and pages F-8 and F-9 of the Greenlee Textron Inc. catalog disclose devices specifically designed to cut DIN rail, which all appear to employ a die particularly shaped to receive DIN rail therethrough, and a hydraulically-powered cutter to cut the DIN rail.
Devices of these types, however, generally are relatively expensive and thus tend to be used in a setup,where a large number of DIN rails of a particular length need to be cut. Such devices thus tend to be prohibitively expensive for smaller panel manufacturers that need to cut a wide variety of lengths, with only a small number of each length. Such devices also tend to have the disadvantage, among others, that, because they use a die to support the workpiece on all sides, they obscure the edge being cut from the device operator's sight. The operator thus must guess exactly where to place a length of DIN rail within the device to accurately trim, i.e., less than 1/2 inch (12.7 mm), from the length, making accurate cuts to within 1/16" (1.6 mm) to 1/32" (0.8 mm) difficult.
Because of the difficulty inherent in cleanly and accurately cutting DIN rail, many panel and center manufacturers use a hand-held hacksaw to cut DIN rail, or bundle DIN rail and cut it with a bandsaw. However, the hacksaw method is very time-consuming, and results in rough edges that typically are filed down by hand. The bandsaw method is faster, but often results in some deformation of the DIN rails, and results in rough edges that also are typically filed down by hand. With either method, it is difficult to cut short lengths of DIN rail without deformation, and, if a length of DIN rail is accidentally cut to a wrong size, it is almost impossible to trim the length down by only a small amount. Such lengths now are usually thrown away. At least one DIN rail manufacturer now manufactures scriven DIN rail that is intended to be broken along one of a series of scriven marks, but such rail generally is very difficult to break cleanly, especially when short lengths are required.
In view of the above, it is an object of the present invention to provide an improved cutting apparatus that is capable of readily cutting a workpiece.
It is another object of the present invention to provide a cutting apparatus that is capable of cleanly and accurately cutting a workpiece having a relatively complex, thin-walled cross section.
Yet another object of the present invention is to provide a cutting apparatus that is capable of cutting a workpiece having a relatively complex, thin-walled cross-section with minimal deformation of the workpiece.
A further object of the present invention is to provide a cutting apparatus that is capable of cleanly, accurately and with minimal deformation cutting a short length of a workpiece having a relatively complex, thin-walled cross section.
A further object of the present invention is to provide a cutting apparatus that is capable of cleanly, accurately and with minimal deformation trim a small amount of material from a workpiece having a relatively complex, thin-walled cross section.